package Network;

import java.io.IOException;
import java.net.*;
import java.util.Scanner;

public class UdpEchoClient {
    private DatagramSocket socket = null;

    // UDP 本身不保存对端的信息,就在自己代码中保存一下
    private String serverIP;
    private int serverPort;

    // 和服务器不同,此处的构造方法是要指定访问的服务器的地址
    public UdpEchoClient(String serverIP,int serverPort) throws SocketException {
        this.serverIP = serverIP;
        this.serverPort = serverPort;
        socket = new DatagramSocket();
    }

    public void start() throws IOException {
        Scanner scanner = new Scanner(System.in);
        while(true){
            // 1. 从控制台读取用户输入的内容
            System.out.println("请输入要发送的信息:");
            if(!scanner.hasNext()){
                break;
            }
            String request = scanner.next();

            //2. 把请求发送给服务器,需要构造 DatagramPacket 对象
            // 构造过程中,不仅要构造载荷,还要设置服务器的IP 和 端口号
            DatagramPacket requestPacket = new DatagramPacket(request.getBytes(),request.getBytes().length,
                    InetAddress.getByName(serverIP),serverPort);

            //3.发送数据报
            socket.send(requestPacket);

            //4.接受服务器的响应
            DatagramPacket responsePacket = new DatagramPacket(new byte[4096],4096);
            socket.receive(responsePacket);

            // 5. 从服务器读取的数据进行解析,打印出来
            String response = new String(responsePacket.getData(),0,responsePacket.getLength());
            System.out.println(response);

        }
    }

    public static void main(String[] args) throws IOException {
        UdpEchoClient client = new UdpEchoClient("127.0.0.1",9090);
        client.start();
    }

}
